Customized PCR-array analysis informed by gene-chip microarray and biological hypothesis reveals pathways involved in lung inflammatory response to titanium dioxide in pregnancy.

Validation of gene-chip microarray results is one of the challenges in genomic studies. The successful use of a custom-designed 96-well polymerase chain reaction (PCR) array to study the unexpected inflammatory effect of environmental titanium dioxide (TiO2) particles on the lungs of pregnant mice, with similar results not seen in control mice, is reported. In our approach, selection of candidate genes for the custom PCR array was informed by prior gene-chip microarray profiling. Results demonstrated multiple upregulation of genes in the lungs of pregnant but not control mice produced by TiO2 exposure. Customized PCR array is a flexible tool that offers the ability to combine the "blind" genome-wide scan with a hypothesis-driven approach, by including both the "candidate" genes for validation positively identified by the microarray and biologically relevant "suspects" that failed to be found in the genomic data. Compared to conventional gene-by-gene qPCR or manufacturer-preset pathway kits, this technique provides a cost-effective and time-saving method of analysis and allows for a strong, easily detectable signal. Genes with confirmed differential expression were further used for pathway analysis and indicated involvement in several biologically relevant pathways including allergy mediator signaling in dendritic cells. Finally, an analytical network was created that will inform further mechanistic studies. The dual purpose of the work was to demonstrate that the novel custom PCR array is a convenient approach to validate the microarray results, and to obtain biologically significant data on TiO2-induced inflammation by following the PCR array with pathway analysis, which provided feasible hypotheses to support future experimental studies.

Characterization of particulate matter for three sites in Kuwait.

Many studies have shown strong associations between particulate matter (PM) levels and a variety of health outcomes, leading to changes in air quality standards in many regions, especially the United States and Europe. Kuwait, a desert country located on the Persian Gulf, has a large petroleum industry with associated industrial and urban land uses. It was marked by environmental destruction from the 1990 Iraqi invasion and subsequent oil fires. A detailed particle characterization study was conducted over 12 months in 2004-2005 at three sites simultaneously with an additional 6 months at one of the sites. Two sites were in urban areas (central and southern) and one in a remote desert location (northern). This paper reports the concentrations of particles less than 10 microm in diameter (PM10) and fine PM (PM2.5), as well as fine particle nitrate, sulfate, elemental carbon (EC), organic carbon (OC), and elements measured at the three sites. Mean annual concentrations for PM10 ranged from 66 to 93 microg/m3 across the three sites, exceeding the World Health Organization (WHO) air quality guidelines for PM10 of 20 microg/m3. The arithmetic mean PM2.5 concentrations varied from 38 and 37 microg/m3 at the central and southern sites, respectively, to 31 microg/m3 at the northern site. All sites had mean PM2.5 concentrations more than double the U.S. National Ambient Air Quality Standard (NAAQS) for PM2.5. Coarse particles comprised 50-60% of PM10. The high levels of PM10 and large fraction of coarse particles comprising PM10 are partially explained by the resuspension of dust and soil from the desert crust. However, EC, OC, and most of the elements were significantly higher at the urbanized sites, compared with the more remote northern site, indicating significant pollutant contributions from local mobile and stationary sources. The particulate levels in this study are high enough to generate substantial health impacts and present opportunities for improving public health by reducing airborne PM.